1. Field of the Invention
The present invention relates to a gas heater, and in particular, to a gas heater of which ignition of gas is accomplished by a ceramic heater.
2. Description of the Prior Art
A gas heater has a high heating efficiency and a low requirement of fuel and hence has been applied to various kinds of heating applications. For example, in a heating operation in a field of hog raising, since hogsties are required to be heated for a long period of time, the gas heater has been effectively used.
In a gas heater of this type, a heater is ordinarily disposed to ignite gas supplied to a burner of the gas heater, thereby achieving ignition of the gas. However, in a case where flame of the gas is extinguished for some reason, after the ignition, the flame extinction must be detected as soon as possible to interrupt the gas supply for safety. Conventionally, a flame sensor has been adopted as means for detecting the flame extinction. The flame sensor is disposed in the flame so as to sense a change in the resistance value thereof at the time of flame extinction, thereby detecting the condition.
In the gas heater of the prior art, the igniting means and the extinction sensing means are separately disposed, which leads to a problem of an increased number of members disposed in the flame. Moreover, when detecting the flame extinction according to the change in the resistance value, since the resistance value varies between different sensors, there arises a problem that it is impossible to set a fixed temperature for the detection of the flame extinction.